Method of Activating a Lithium Secondary Battery Including a Positive Electrode Additive

Abstract

A method of activating a lithium secondary battery and a lithium secondary battery prepared by the same are disclosed herein. In some embodiments, a method includes charging the lithium secondary battery to a state of charge (SOC) of 90% or more in an activation step, wherein the lithium secondary battery having an electrode assembly comprising a positive electrode and an electrolyte, wherein the positive electrode comprises a mixture layer having a positive electrode active material and a positive electrode additive, and degassing the lithium secondary battery during the activation step to removing gas inside the secondary battery. The method is advantageous in that a side reaction gas can be removed by performing degassing during activation, thereby forming a stable SEI film on the electrode surface to improve battery performance and battery safety.

1 . A method of activating a lithium secondary battery, comprising:
 charging the lithium secondary battery to a state of charge (SOC) of 90% or more in an activation step, wherein the lithium secondary battery having an electrode assembly comprising a positive electrode and an electrolyte, wherein the positive electrode comprises a mixture layer having a positive electrode active material and a positive electrode additive; and   degassing the lithium secondary battery during the activation step to removing gas inside the secondary battery.   
     
     
         2 . The method of  claim 1 ,
 wherein the activation step comprises two or more activation steps, and   wherein the degassing process is performed between each of the two or more activation steps.   
     
     
         3 . The method of  claim 1 , wherein the degassing performed two or more times during the activation step. 
     
     
         4 . The method of  claim 1 ,
 wherein the activation step further comprises:   a first activation step wherein charging is performed at a rate of 0.5 C or less up to a first level of SOC; and   a second activation step wherein charging is performed at a rate of greater than 0.5 C up to a second level of SOC, wherein the second level of SOC is greater than the first level of SOC.   
     
     
         5 . The method of  claim 1 ,
 wherein the activation step further comprises:   a first activation step wherein the lithium secondary battery is charged to an SOC of 20% or less;   a second activation step wherein the lithium secondary battery is charged from an SOC greater than 20% to 40% or less;   a third activation step wherein the lithium secondary battery is charged from an SOC greater than 40% to 70% or less; and   a fourth activation step wherein the lithium secondary battery is charged to an SOC of 90% or more,   wherein the degassing is performed between at least one of the first and second activation steps, the second and third activation steps, or the third and fourth activation steps.   
     
     
         6 . The method of  claim 5 , wherein the degassing performed between the first and second activation steps, the second and third activation steps, and the third and fourth activation steps. 
     
     
         7 . The method of  claim 5 , wherein
 during the first activation step, charging of the lithium secondary battery is performed at a rate of 0.5 C or less, and   wherein, during the second to fourth activation steps, charging of the lithium secondary battery is performed at a rate of more than 0.5 C.   
     
     
         8 . The method of  claim 1 , wherein the activation step further comprises:
 pressurizing the lithium secondary battery.   
     
     
         9 . The method of  claim 1 , wherein the activation step is performed at a temperature of 40° C. to 70° C. 
     
     
         10 . The method of  claim 1 , wherein the positive electrode additive is a lithium cobalt oxide represented by the following Chemical Formula 1:
   Li p Co (1−q) M 1   q O 4    [Chemical Formula 1]
   wherein,   M 1  is one or more elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo,   5≤p≤7; and   0≤q≤0.5.   
     
     
         11 . The method of  claim 10 , wherein, in Chemical Formula 1, M 1  is Zn, and 0.2≤q≤0.4. 
     
     
         12 . The method of  claim 1 , wherein the content of the positive electrode additive is 0.1 to 5 wt % based on the total weight of the mixture layer. 
     
     
         13 . The method of  claim 1 , further comprising:
 aging the lithium secondary battery at a temperature of 40° C. to 80° C. after the activation step.   
     
     
         14 . A lithium secondary battery including an electrode assembly including:
 a positive electrode;   a negative electrode;   a separator disposed between the positive electrode and the negative electrode; and   an electrolyte,   wherein the positive electrode comprises a positive electrode current collector and a positive electrode mixture layer, wherein the positive electrode mixture layer comprises a positive electrode active material, a positive electrode additive represented by the following Chemical Formula 1, a conductive material, and a binder, and   wherein the positive electrode active material is a lithium nickel composite oxide represented by the following Chemical Formula 2:
   Li p Co (1−q) M 1   q O 4    [Chemical Formula 1]
 
   Li x [Ni y Co z Mn w M 2   v ]O u    [Chemical Formula 2]
 
   wherein,   M 1  is one or more elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo,   5≤p≤7,   0≤q≤0.5,   M 2  is at least one element selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo,   1.0≤x≤1.30,   0.1≤y<0.95,   0.01<z≤0.5,   0.01<w≤0.5,   0≤v≤0.2, and   1.5≤u≤4.5.   
     
     
         15 . The battery of  claim 14 ,
 wherein the negative electrode comprises a negative electrode current collector and a negative electrode mixture layer positioned on the negative electrode current collector,   wherein the negative electrode mixture layer contains a negative electrode active material, and   wherein the negative electrode active material contains a carbon material and a silicon material.